The present invention concerns a light fixture with a rod-shaped light source, and on both longitudinal sides of the light source, extending over it, there are concave reflectors that have a curvature such that all the light rays reflected across the light source emerge in the transverse direction either directly or after reflection at an angle that is steeper than a light-specific masking angle .alpha., and with lamellae that have an approximately V-shaped cross section and run across the middle vertical longitudinal plane of the light source and have reflecting concave side surfaces that have a curvature such that all the light rays eflected in the longitudinal direction of the light source will emerge in the longitudinal direction either directly or after reflection at an angle which is steeper than a light-specific masking angle .beta., and the top sides of the lamellae are covered by a reflective cover.
In light fixtures of the above-mentioned type, the surface of the lamellae running across the light source is designed to be reflective, so that even light rays striking the lamellae from above can be reflected and can finally emerge out of the light. Otherwise, the efficiency of such light fixtures would be reduced substantially because the lamellae must be spaced at relatively short distances from each other if the desired goal of masking light rays emerging at a shallow angle is to be achieved. An important drawback of the known design, however, is that the light rays reflected from the top sides of the lamellae emerge for the most part at a shallower angle than the incident angle, and this leads to a mirror image of the light source for the observer, and this ultimately leads to a glare effect. This mirror image is especially disturbing in working with display screens. To prevent this problem, proposals have already been made for blackening the top side of the lamellae or designing them so as to be open at the top. Both cases, however, lead to the above-mentioned loss of efficiency, which may amount to as much as 20 %.
In addition, a light fixture with an elongated lamp is known from German Utility Patent No. 81 06 507, in which case to avoid extreme brightness in the vicinity of the reflector sections above the lamellae, the covers to the lamellae have sloping sections in the space above the lamp that are inclined toward the vertical plane of the lamp. These sloping sections may have a concave curvature, for example. Owing to this design, some of the rays reflected by the light source may be reflected into the space above the light source by the inclined covers, but precisely in the critical areas where the lamellae meet the reflectors, there is still a problem with reflections leading to the undesired brightness.
This invention is based on the the goal of improving a light fixture of the type described initially, so that the entire cover area of the lamellae will reflect incident beams of light in such a way that complete freedom from glare is achieved.
According to this invention, this is achieved by shaping the lamellae so as to form two lamellar sections that are symmetrical with respect to the middle longitudinal plane so that their flat surfaces form an angle of inclination with the longitudinal plane that corresponds approximately to the masking angle .alpha., and they have the opposite slopes and are in tangential proximity to the light source, although without coming in contact with it, and extend as far as the reflectors. According to this invention, the cover of the lamellae is not curved, but instead the cover of the lamellae is flat and the lamellae themselves are inclined with respect to the longitudinal plane of the light source, namely from below the light source up to above the light source. This design of the lamellae according to this invention assures that reflections in the interfering angle of view range which is defined by the masking angle .alpha. are avoided with these reflectors because the lamellae run in this range. Below the masking angle .alpha. complete freedom from glare is achieved according to this invention without any mentionable loss of efficiency due to absorption of the light rays striking the top side of the lamellae. The best solution theoretically is a flat top side which would be in tangential contact with the light source. However, for structural and tolerance reasons, such contact of a light source with the lamellae is impossible. For this reason, the present invention proposes a tangential approach of the top side of the lamellae to the light source, but maintaining a distance which is determined by the design.
This invention will now be illustrated in greater detail with reference to the figures.